Currently, with the promotion of production line in liquid crystal field, the sizes of substrates to be produced become ever bigger and the requirement of the defect-free rate becomes ever higher, which cause a series of problems. For example, during the fabricating process of a color filter substrate, because the color filter substrate has too large an area, in-plane pressure distribution across a color filter substrate is uneven, which results in a limitation on the product design.
Particularly, during the fabrication of post spacers, as illustrated in FIG. 1, an area of a mask plate 2 which is configured to fabricate the post spacers is relatively large as a color filter substrate 1 has too large an area. A central region of the mask plate 2 will bend and sag due to gravity, causing an exposing distance h1 of a peripheral region of the mask plate 2 being 50 μm to 70 μm larger than an exposing distance h2 of the central region. When a positive photoresist is used, the photoresist in an exposed region is removed through a developing process and the post spacers to be retained are disposed in a non-exposing region, thus a height of the formed post spacers will not be affected by the exposure process. However, in the case that a negative photoresist is used, the post spacers to be retained is disposed in the exposing region and the photoresist in non-exposing region is removed through a developing process, thus the height of the formed post spacers made from the negative photoresist is affected by the exposure process. As a result, a height of post spacers in the central region is larger than that of post spacers in the peripheral region, thereby compromising the uniformity of the color filter substrate.